Method of manufacturing dry aluminum capacitors, and capacitors obtained by this method

ABSTRACT

A method of manufacturing dry aluminium capacitors wherein anode elements are punched from an aluminium plate and are successively etched, formed and provided with a semiconductor layer. After the covering with a graphite layer and a silver layer, an anode wire is connected to the anode element and a cathode wire is connected to the silver layer. Each anode element consists of a strip of coherent plates which, after etching and prior to forming, are folded one on the other so as to form a stack. Each strip is connected to a carrier ribbon by a connection tag on which a dam is formed which projects from the plane of the carrier ribbon.

United States Patent [191 Heier et a1.

[ METHOD OF MANUFACTURING DRY ALUMINUM CAPACITORS, AND CAPACITORS OBTAINED BY THIS METHOD [75] Inventors: Jan Heier,l immasingel, Eindhoven;

Waltherus Andreas Zoethout, Zwolle, both of Netherlands [731 Assignees U.S. Philips Corporation, New

York, NY.

22 Filed: Mar. 14,1973

21 Appl. No.: 340,965

[30]- Foreign Application Priority Data Mar. 20, 1972 Netherlands 7203719 [52] US. Cl. 29/570 [51] Int. Cl B01j 17/00 [58] Field of Search 29/570, 25, 42

[56] References Cited UNITED STATES PATENTS June 25,1974

Brill 29/570 Matsuo 29/570 Primary ExaminerW. Tupman Attorney, Agent, or Firm-Norman N. Spain; Frank R. Trifari 5 7] ABSTRACT A method of manufacturing dry aluminium capacitors wherein anode elements are punched from an aluminium plate and are successively etched, formed and provided with a semiconductor layer. After the covering with a graphite layer and a silver layer, an anode wire is connected to the anode element and a cathode wire is connected to the silver layer. Each anode element consists of a strip of coherent plates which, after etching and prior to forming, are folded one on the other so as to form a stack. Each strip is connected to a carrier ribbon by a connection tag on which a dam is formed which projects from the plane of the carrier ribbon.

' 3 Claims, 18 Drawing Figures PATENTED JUN 2 5 1974 I 3.819.340 SHEET 3 BF 4 METHOD OF MANUFACTURING DRY ALUMINUM CAPACITORS, AND CAPACITORS OBTAINED BY THIS METHOD The invention relates to a method of manufacturing dry aluminium capacitors, wherein anode elements are punched from an aluminium plate, each anode element being connected to a continuous carrier ribbon and being etched, formed and provided with a semiconductor layer in succession and, after having been covered with a graphite layer and a silver layer, being separated from the carrier ribbon, after which an anode wire is connected to the anode element and a cathode wire is connected to the silver layer, the capacitors thus obtained ultimately being provided with an envelope.

In capacitors manufactured by a known method of this kind, the anode elements comprise only a single aluminium plate, so that as the capacitance increases the relative dimensions become'more unfavourable, with the result that the field of application and the usability of these capacitors are limited.

The present invention has for its object to provide a method by which capacitors of different capacitance and compact dimensions can be readily manufactured in a costsaving manner.

This object is mainly achieved according to the invention in that the anode elements are obtained by punching from the aluminium plate strips of coherent plates which extend perpendicular to the longitudinal direction of the carrier ribbon, the said strips being connected to the carrier ribbon via a connecting tag, the plates of a strip after etching and prior to forming, being folded one on the other so as to form a stack, the elements being separated'from the carrier ribbon by cutting the connecting tag.

By folding a number of plates one on the other so as to obtain a stack which fonns the anode element, capacitors are obtained which are very compact and which have a ratio of length, width and thickness which is very favourable for practical usability, in particular for higher capacitances. By varying the number of plates which are folded on each other, capacitors of different capacitance can be readily manufactured.

It is to be notedthat it is known per se to assemble capacitors of different capacitance by folding a carrier ribbon on, which elementarycapacitors are formed; however, the folding operation is performed only after complete treatment of the elementary capacitors, it being necessary to interconnect the cathodes of the elementary capacitors.

In a preferred embodiment of the method according to the invention, a dam projecting from the plane of the carrier ribbon is formed on the connecting tags priorto the forming. The part of the connecting tag which serves for the subsequent connection of the anode wire must remain bare. The dam prevents the cathode material from creeping up too high when the anode element is dipped into theliquid cathode material so as to form the semiconductor layer, with the result that any electrical short-circuits are counteracted. Due to the dam on the connecting tags, the temporary coating of the connection part is superfluous; this is in contrast with the said known method where part of the surface of the anode elements must be covered with an insulating coating'prio'r to forming in order to shield this part, intended for the subsequent connection of the anode wire, from the semiconductor material; this coating must be dried after deposition and be partly removed again following the treatment of the anode element.

It is to be noted that it is known per se to provide the connection wires of electrical components with a shoulder or bracket; however, this shoulder only serves as an abutment when the component is mounted in a printed circuit board. In the mounted condition, the end of the connecting tag of the capacitor according to the invention bears on the printed circuit board.

In another preferred embodiment of the method according to the invention, the connecting tags are cut to a length such that, after fixation of the anode wire on the connecting tag, the part of the anode wire which projects from the connecting tag is not covered with lacquer when the envelope is provided by lacquering. Due to the connecting tag, the level of the lacquer layer can be accurately defined both on the anode wire and on the cathode wire. When the capacitor is mounted in a printed circuit board, there will be no problems caused by the presence of lacquer on the wires when the connection wires are soldered. The connecting tag must have a length which is sufficient to obtain adequate mechanical strength of the connection of the anode wire to the connection tag by the provision of a lacquer layer on the connecting tag as far as its free end.

The capacitors obtained by the method according to the invention are very compact and are characterized by the plates which are folded one on the other to form a stack; by the dam on the connecting tag, and by the absence of lacquer on the projecting part of the anode wire.

The invention will be described in detail with reference to the drawings. In the drawings:

FIGS. 1 to 14 are diagrammatic representations of various stages of the method according to the invention;

I FIG. 15 is a sectional view at an increased scale of a part of the capacitor obtained by the method according to the invention;

FIGS. l6, l7 and 18 are a front view, a side view and a bottom view, respectively, of the finished capacitor.

' Some Figures of the drawing show several treatment phases for the sake of simplicity. From a plate 1 of very pure aluminium a band 3 is punched which consists of a continuous carrier ribbon 5 and anode elements 7, each anode element being connected to the carrier ribbon 5 via a connecting tag 9. As a result of the defined distance and the coherence of the anode elements, a band of this kind is suitable for a continuous movement process as well as for an intermittent process where the band is cut into pieces.

According to the invention, each anode element consists of a strip 11 of punched plates 13 which are interconnected by constricted connecting bridges '17 which are obtained by means of notches 15 (FIG. 1). On the connecting tags 9 a U-shaped dam 19 is formed, preferably during or immediately after the punching operation, in any case before the forming, the said dam projecting from the plane of the carrier ribbon 5 at a sharp bend (FIG. 2). The surface 21 which faces the plates 13 is perpendicular to the plates. The part 23 of the connecting tags'9 between the dam l9 and the carrier ribbon 5 serves for the subsequent connection of an' In order to increase the surface area of the plates 13, the anode elements 7 are subsequently electrochemically etched by suspending them in a pickling bath 25 of known composition (FIG. 3).

According to theinvention, the plates 13 of a strip 11 are subsequently folded one on the otherto form a stack 27. This phase is shown in the FIGS. 4, and 6. The folded plates will be situated below the face 21 of the dam 19. The width of the dam 19 in a direction perpendicular to the plane of the plates 13 is dependent of the number of plates folded on each other and is substantially equal to the width of the stack 27.

FIG. 6 shows that a clearance remains between the plates 13 after folding to allow further treatment of the stacked anode element 7. In the embodiment shown, each anode element 7 comprises five plates 13. The number of plates to'be punched and folded on each other can be varied, and is dependent of the desired capacitance of the capacitor to be manufactured. By assembling the anode elements in the described manner, capacitors are obtained which have, particularly in the case of higher capacitances, very compact dimensions which are acceptable and usable in practice.

The described dam 19 could also be formed during the folding operation; in any case, the darn must be provided before the next treatmenttakes place, i.e. the forming which is shown in FIG. 7. In this treatment phase, an aluminium oxide layer 31 which serves as a dielectric in the finished capacitor is formed on the plate 13 by anodic oxidation by dipping the anode elements 7 as far as the dam 19 into a bath 33 of a known forming electrolyte.

In the subsequent treatment phase, shown in FIG. 8, a layer 35 of semiconductor material, manganese dioxide which acts as the cathode is deposited on the dielectric 31. In order to deposit this semiconductor material in the pores of the etched aluminium (aluminium oxide), the anode elements 7 are impregnated with manganese nitrate by dipping in a bath 37 containing a manganese nitrate solution. This material is subsequently subjected to pyrolysis at a temperature of between 200 and400 C, during which the manganese nitrate is converted into manganese dioxide which establishes intimate contact with the dielectric. During this operation it must be prevented that the part 23 of the connecting tag 9 which serves for the connection is covered with manganese dioxide. In the method according to the invention this is readily achieved by means of the dam 19 which prevents manganese dioxide formed during the pyrolysis process from coming into contact with the connection part 23 of the connecting tags 9. This process is repeated a few times so as to obtain proper filling. After each pyrolysis, the dielectric 31 which is slightly attacked by the pyrolysis is restored by repeated forming in'a bath 39 (FIG. 9). The repeated forming is restricted to those parts of the aluminium oxide layer where non-oxidized aluminium becomes exposed due to the formation of cracks. The repeated forming is possible as a result of the porosity of the manganese dioxide.

In order to enable a connection wire to be soldered to the cathode layer 35 and to keep the contact resistances as low as possible, the manganese dioxide is covered with a graphite layer 41 and with a silver layer 43 by successively dipping the anode elements in a graphite suspension 45 and a silver suspension 47, as is diagrammatically shown in FIG. 10. After these treatments, the connection part 23 of the connecting tags 9 is still bare.

Subsequently, the silver-plated elements .7 withthe projecting bare connection part 23 are separated from the carrier ribbon 5 (FIG. 11). Each element is provided with an anode wire 51 which is welded to the projecting connection part 23 of the connecting tag 9, and with a cathode wire 53 which is soldered to the silver layer 43 (FIG. 12). Finally, the elements are provided with a lacquer layer 55 by dipping in a lacquer bath 57 (FIG. 13). By dipping the elements into the bath 57 exactly as far as the end 58 of the connecting tag 9, it is prevented that lacquer comes into contact with the free projecting part of the anode wire 51. When mounted on a printed circuit board, the capacitor bears on the end 58 of the connecting tag 9. Subsequently, the elements 7 are codedand the anode wire 51 and the cathode wire 53 are cut to the desired length, after which the finished capacitor 59 can be tested.

FIG. 15 is a sectional view of a part of the capacitor 59 according to the invention, both sides of each plate 13 accommodating the dielectric 31, the semiconductor cathode layer 35, the graphite layer 41, the silver layer 43, and the lacquer layer 55.

FIGS. 16, 17 and 18 are different views of the finished capacitor 59 with the anode wire 51 and the cathode wire 53. The lacquer layer 55 extends as far as the free end of the connecting tag 9. Clearly shown is the straight end 58 of the connecting tag 9 on which the capacitor bears when mounted on a printed circuit board.

What is claimed is:

1. A method of manufacturing dry aluminium capacitors wherein anode elements are punched from an aluminium plate, each anode element being connected to a continuous carrier ribbon and being etched, formed and provided with a semiconductor layer in succession and, after having been covered with a graphite layer and a silver layer, being separated from the carrier ribbon after which an anode wire is connected to the anode element and a cathode wire is connected to the silver layer, the capacitors thus obtained ultimately being provided with an enevelope, characterized in that the anode elements are obtained by punching from the aluminium plate strips of coherent plates which extend perpendicular to the longitudinal direction of the carrier ribbon, the said strips being connected to the carrier ribbon via a connecting tag, the plates of a strip, after etching and prior to forming, being folded one on the other so as to form a stack, the elements being separated from the carrier ribbon by cutting the connecting tag.

2. A method as claimed in claim 1, characterized in that a darn projecting from the plane of the carrier ribbon is formed on the connecting tags prior to the form- 3. A method as claimed in claim 1, characterized in that the connecting tags are cut to such a length that, after fixation of the anode wire on the connecting tag, the part of the anode wire which projects from the connecting tag is not covered with lacquer when the envelope is provided by dip lacquering.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION v Pa nt 3,819,340 (PI-IN 6191) Dated June 25,1974

lnventofls) JAN HEIER ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Title page:

Item [75] ,This item should read:

[75] Inventors: Jan Heier, Eindhoven; Waltherus Andreas Cornelis Mikkers, Zwolle;

Robert Anton Zoethout, Zwolle, all of Netherlands Signed and sealed this 29th day of 0ctober 1974.

( L) n o r Attest:

McCOY M. GIBSON JR. Attesting Officer C. MARSHALL DANN Commissioner of Patents 732 3 v} UNITED STATES "PATENT OFFICE CERTIFICATE OF CORRECTION I Patent No. 3, 819, 340 (PI-11$ 6191) Dated June 25, 1974- Inventofls) JAN HEIER ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Titlepa g e:

Item [75] ,This item should read:

[75] Inventors: Jan Heier, Eindhoven; Waltherus I Andrea's Cornelis Mikkers, Zwolle;

Robert Anton Zoethout, Zwolle I all of Netherlands I I Signed and sealed this 29th day of 0ctober 1974.

Attest: I

McCOY M. GIBSON JR. c. MARSRALL 1mm Attesting Officer Commiss10ner of Patents 

2. A method as claimed in claim 1, characterized in that a dam projecting from the plane of the carrier ribbon is formed on the connecting tags prior to the forming.
 3. A method as claimed in claim 1, characterized in that the connecting tags are cut to such a length that, after fixation of the anode wire on the connecting tag, the part of the anode wire which projects from the connecting tag is not covered with lacquer when the envelope is provided by dip lacquering. 